He meant whether it's on difficulty setting A (slow missiles) or B (fast missiles), which is what those buttons change.

There's no way to see which mode it's on besides looking at how fast your missiles are. The difficulty setting was controlled by an actual physical switch, meaning you could tell what it was set to by just looking at the switch, so there was no need to have any on-screen indicator for it any more than there's a need to have an on-screen indicator for whether your controller is connected.